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Sunday, 26 October 2008

Kernel booting - continued

The Ubuntu install on the laptop is now complete. No more Windows :) After a quick and painless install via USB flash keyring, I followed the Wiki to setup the laptop for development. A few steps we're missing in the Wiki setup guide (particularly the GDB/Insight install), so that Wiki page has been updated.

I also spent some time looking into Kernel booting. The 2.6.23 kernel decompresses the zImage, it gets to the 'Done' stage, but goes no further than that. I've checked the ldatags side of uMon and compared that to the setup code in the kernel, and they tied together (as they did in 2.6.22). I've also incrementally patched the 2.6.22 kernel up from the sub-version 6 in the VC CVS, all the way up to, and it boots fine (except for the usual MTD issues). It's only when I move to 2.6.23 that the boot fails.
So it looks like I need to debug further into the boot sequence. Potentially using the 3 LEDs on the VCMX212 board as a limited binary sequence counter to step through the boot sequence. I need to find some time to see whether I debug the kernel startup/boot via GDB. Just need a way of setting up the ATAG info to pass to the kernel.

So I've got a choice. Continue advancing the kernel versions and sorting out the booting issues, to hopefully get to a point whether the MTD problems sort themselves out. Or, stay with 2.6.22 (with MTD/JFFS2 patches) and work out why it is spewing so many errors out (and once into BusyBox, why it is so unstable).....

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